Air Conditioning boiling Hot ?

[Guest]

Hi,

Hope someone out there can help me. I have a 1988 944 Turbo and the air con is playing up.

If I set the dial to as cold as possible, the usual semi cold air will come out of the vents. If I then also press the Air Con button (which does light up), that same air turns red hot. Everything else stays as it was. If I then flick the air con switch off - it goes back to semi cold as I would expect. Anyone has this problem before or know what this means ?

Thanks guys.

GH.

 

[Fen]

I've not seen that specific problem before, but a common failure that leads to erratic tempreature control is a broken clip that holds 2 linkage rods together between the govebox liner and the middle of the dash. You might be able to see it if you contort yourself into the footwell, or it's easy to take out the glovebox liner - remember to take out the interior light fuse first or you'll very likely blow it when you remove the liner as the light usually shorts on the dash.

 

[944turboS]

While you've got the glove box out follow the air sampling pipe & clean out the little fan unit on the other end, it's probably quite mucky after years of use but no maintenance.

 

[Fen]

That's a fair sumary of how it works, Andrew, but I can't see how the evaporator can act as a heater matrix and actively warm the air - all that can be in it is evaporating refrigerant which chills the evaporator (it's a small radiator in the blower box) and draws heat from the air passing over it to the cabin hence cooling it or nothing which means it can't change the temperature of the air as it will itself be at ambient temperature. The desired cabin temperature is achieved by blending hot air drawn through the heater matrix with cold air drawn through the scuttle and optionally cooled further by the air-con evaporator if the a/c is running. If it isn't a linkage rod problem (and I don't think it is, but it's common, easy to check and cheap to fix if it is so worth a try as a first step) then what I am sure is happening is that the electronics in the heater control unit "expect" the incoming cool air to suddenly be much cooler when the air-con has been turned on, but it is actually no cooler as I suspect the compressor is not running. That being the case it will even out to the same sort of temperature as before when the control unit realises the cool air is not as cool as expected. Does the compressor solenoid click as the clutch engages when you turn the a/c on? Do the revs change momentarily at the same time? If no to both then the compressor isn't working, possibly because there is not enough pressure in the system to allow it to start or possibly because some component has failed. That being the case it's time for an air-con specialist to look at it.

 

[carlmthompson]

After mine was standing for the best part of last year, it's now particularly poor also. It still runs, and has been serviced recently (2002), but I'm not sure wether it's worth charging again if I'm only doing 3k a year!

 

[Guest]

Check the aircon relay too. I had some problems with mine a while back (i don't remember whether it pumped out hot air or what exactly!) One raly later, and wey-hey brrrrr!

 

[Siggy]

If I set the dial to as cold as possible, the usual semi cold air will come out of the vents. If I then also press the Air Con button (which does light up), that same air turns red hot.

Will it do that when the engine is cold?

Check that the air con pump is actually turning when you switch it on.

Does sound like its a heater problem rather than a A/C problem

If you are not running the car very often run the air con all the time. Gas will escape throught the seals if the pump is not running for long periods.

Dave